Our correspondent at United States Central Command in Qatar takes stock of coalition strategy and tactics:

Baghdad

Officials here say the intention is to cut the city off from the rest of the country. This is not exactly "encircling" the city - the Americans don't have enough troops for that - but it does mean controlling all the major routes in and out of Baghdad. The Tikrit road has already been severed by special forces.

Meanwhile, elements of the US Army's V Corps are working their way clockwise around the city, from the west to the north. A similar, anti-clockwise move is under way on the city's eastern flanks, involving the 1st Marine Expeditionary Force. It's likely to be a little while before this operation is complete - perhaps by Monday.

At the same time, US forces continue to probe the defences of Baghdad, following Saturday's aggressive sweep through the south-western reaches of the city (which CentCom officials say killed at least 2,000 Iraqi fighters - a figure disputed in Baghdad). There have been sharp exchanges of fire in several parts of the city during Sunday.

Officials won't say how many American troops are now massed around the city, but with around 7,000 at the airport, the figure is probably around 20,000.

Privately, some British officials have voiced concern about the apparently heavy-handed tactics adopted by the Americans as they stormed through the city on Saturday. They contrast this with the much more cautious approach of the British in Basra.

"There's already enormous and deep suspicion throughout the Arab world about why the Americans are doing this," one official said. "The worry is that you'll feed every anti-American suspicion by going in there and breaking all the china."

Basra

After a couple of weeks of probing and reconnaissance, backed up by extensive use of special forces, aerial surveillance and psychological operations, British commanders decided to switch tactics on Sunday morning.

Three elements of the UK's 7th Armoured Brigade (the Desert Rats) moved into the city from three positions to the west. The Royal Scots Dragoon Guards drove in with their Challenger 2 main battle tanks. 1st Battalion, the Royal Regiment of Fusiliers and 1st Battalion, the Black Watch, went in aboard Warrior infantry fighting vehicles.
Later in the day, 3 Commando Brigade began another push forward from positions south of the city.

Officials say that after "a lot of prodding", there were clear signs that the city's defenders were losing heart. Reports of widespread looting suggested that law and order was breaking down in the city.

Planners were also buoyed by news that a US air strike on Saturday may have killed the man in charge of defending the south, Ali Hassan al-Majid, known in the west as "Chemical Ali". One or more of his bodyguards have already been positively identified.

So far, fighting appears to have been light, but British officials are not complacent. They're acutely aware that controlling a city of 1.5 million people is likely to present problems for such a small force.

Capitulation

US officials here say that two divisions of regular troops, based south-east of Baghdad, have indicated their willingness to capitulate. "Certain contacts" have been made, but commanders will be wary, following the early experience around Basra, where the 51st Mechanised Div. appeared willing to surrender but some soldiers fought on.

The same officials say that Iraqi command and control is now "almost non-existent," with the result that much of the resistance seems chaotically organised.

A message carried on Iraq's satellite TV channel, purporting to come from Saddam Hussein, urges soldiers to join "any unit that is similar to that in his formation and be deployed within this unit until further notice." Another sign, it seems, that Iraq's military structure is collapsing.

Evidence of terror links?

For the first time since the campaign began, US commanders spoke of unearthing evidence which they believe points to a link between Saddam Hussein's government and terrorism.

Brigadier General Vince Brooks said that US Marines had overrun a training camp near Salman Pak, south of Baghdad, and destroyed tanks and armoured personnel carriers.

He said US troops had encountered fighters from several countries, including Sudan and Egypt, adding that the find showed "linkage between this regime and terrorism." Before the war, US officials repeatedly stressed that they had evidence of such links.

Iraqi opposition fighters

The US military has flown as many as 1,000 "opposition fighters" into southern Iraq. The force appears to be under the control of Ahmed Chalabi, leader of the Iraqi National Congress. The force has been described as "the beginning of the free Iraqi army," by General Peter Pace, vice-chairman of the US Joint Chiefs of Staff.

The INC says the force will join in "removing the final remnants of Saddam Hussein's Baathist regime." It's likely the force has been flown to the airbase at Talil, just outside Nasiriya.

Mr Chalabi is much loved by the US Department of Defence, but held in much lower regard by the State Department. His role in post-war Iraq is likely to be the subject of controversy. British officials privately question whether he commands any real respect within Iraq. They also doubt that his fighters will add much.